Arrangement for disengaging threading dies in a threading die head

ABSTRACT

For disengageably securing threading dies in the head of a thread-cutting machine or a similar device, axially extending holding bolts are provided in a die carrier for locating the dies in the threading position. The ends of the holding bolts spaced from the dies are secured to a flange displaceably mounted on the die carrier. A slide bushing is in threaded engagement with the flange and extends axially through a bore in the die carrier. A sensing bolt extends through the slide bushing and has a contact surface on one end for contacting a workpiece being threaded. Springs are located in the die carrier for biasing the flange away from the dies. While the workpiece is being threaded, the slide bushing is held against displacement in the axial direction relative to the die carrier, however, when the threading action is completed the sensing bolt is displaced axially and releases the locking action between the slide bushing and the die carrier. As a result, the flange connected to the slide bushing is biased by the spring so that the holding bolts release the dies from the threading position.

O llnited States Patent 91 [111 3,735,436 Louys 1 51 May 29, 1973 1ARRANGEMENT FOR DISENGAGING 3,580,690 5/1971 McClure ..10/96 R THREADINGDIES IN A THREADING DIE HEAD Primary ExaminerCharles W. Lanham AssistantExaminer-E. M. Combs [75] Inventor fi Louys schafihausen Attorney-DavidToren, Bernard X. McGeady and let an Leo Stanger [73] Assignee: GeorgFisher Aktiengesellschaft,

Schaffltausen, Switzerland ABSTRACT [22] Filed: June 9, 1972 Fordisengageably securing threading dies in the head of a thread-cuttingmachine or a similar device, axially [2]] Appl' 261531 extending holdingbolts are provided in a die carrier for locating the dies in thethreading position. The [30] Foreign Ap li ti n P i it D ends of theholding bolts spaced from the dies are secured to a flange displaceablymounted on the die June 14, 1971 Switzerland ..8625/71 Garden A Slidebushing is in threaded engagement with the flange and extends axiallythrough a bore in [52] LS. Cl. ..10/96 R, 10/120,408/148 the i Garden ASensing bolt extends through the [51] "B23g 5/12 slide bushing and has acontact surface on one end for [58] Field Of Search ..10/89 H, 89 P, 94,contacting a workpiece being threaded Springs are 10/95 96 123 locatedin the die carrier for biasing the flange away 123 S; 279/66 6975;408/148 153 from the dies. While the workpiece is being threaded, theslide bushing is held against displacement in the [56] References C'tedaxial direction-relative t0 the die carrier, however, when the threadingaction is completed the sensing UNITED STATES PATENTS bolt is displacedaxially and releases the locking action 2,130,181 9/1938 Hogg ..10/95between the slide bushing and the die carrier. As a 2,135,067 11/1938Breitenstein ..10/95 result, the flange connected to the slide bushingis Breitenstein biased the so that the bolts release 2,471,250 5/1949Strickland ..10/95 the dies from the threading position. 1 2,746,0665/1966 Finn et al. ..10/95 16 Claims, 3 Drawing Figures 1 fee, 1 2v v 11 A v 8 i 5 26 7 1 f a 0: y A 6 1 1 l T i l 19 1 1 1:1 2t l T 9 7 l 1 Iy I 16 l8/ l' I 10 l lla ARRANGEMENT FOR DISENGAGING THREADING DIES IN ATHREADING DIE HEAD SUMMARY OF THE INVENTION The present invention isdirected to a die head or chuck for disengageably securing threadingdies in the threading position and, more particularly, it concerns anarrangement mounted within a die carrier for disengaging the threadingdies from the threading position.

In one known threading die head, a setting ring is positioned within andis rotatable relative to a die carrier and holds the threading dies. Thesetting ring includes a cam, and a compression spring is associated withthe cam. The compression spring biases the setting ring into engagementwith the contact or abutment surface of a follower and thus'holds thethreading dies in the threading position. For determining the length ofa thread cut into a pipe or workpiece, a sensing element checks thethread length and whena predetermined length has been reached, it liftsthe follower from the cam of the setting ring. When this occurs, thecompression spring rotates the setting ring and the dies are lifted outof the threading position.

In this previously known threading die head, a portion of the sensingand release mechanism used in restoring or resetting the threading dies,is arranged in an eccentric and projecting manner on the die carrier.Such an arrangement is dangerous, since it tends to cause injury topersonnel asthe threading die head rotates and it is alsodisadvantageous, because the resetting action can be performed only whenthe threading die head is at rest.

Another known embodiment of a threading die head includes a setting bodyfor the threading dies in which the positions of the setting body aredetermined by coupling members. The setting body is biased by arestoring spring which tends to move it into a position in which thethreading dies are displaced from the threading position. For actuatingthe biasing action of the restoring spring, a sensing arrangement isprovided to de- When a predetermined length of thread has been cut, thecoupling members are released and, due to the biasing action of therestoring spring, the setting body is turned so that the threading diesare displaced from the threading position. To restore the threading diehead while tensioning the restoring spring, it is necessary to use a keywhich is inserted radially into an opening in the setting body. As withthe other known embodiment mentioned above, the threading die head canonly be restored into the threading position when the arrangement iscompletely at rest.

Therefore, it is the primary object of the present invention to providea self-releasing threading die head arrangement which can be returned tothe threading position without any danger of accident or injury, evenduring rotation. Due to this arrangement, accelerated threading ispossible.

In accordance with the present invention, a threading die head used in athread-cutting machine or device has a plurality of disengageablethreading dies mounted in a die carrier. The dies are held in thethreading position by cams located on the ends of holding bolts whichextend through the die carrier. The die carrier has an annular shape andforms an axially extending bore. At the end of the die carrier, spacedfrom the dies, a flange is positioned about the bore and springs mountedin the termine the length of the thread cut in a workpiece.

die carrier bias the flange away from the dies. A slide bushing is heldin threaded engagement with the flange and extends into the bore throughthe die carrier. Extending through the slide bushing is a sensing boltand one end of the bolt extends beyond the slide bushing and has acontact surface arranged to contact the end of a workpiece beingthreaded. During the threading operation, balls fitted into openings inthe slide bushing engage in a groove within the die carrier and hold theslide bushing and flange against axial displacement relative to the diecarrier. When the threading operation is completed, the sensing bolt isdisplaced axially and has a groove into which the locking balls in theslide bushing are displaced so that the slide bushing and flange are nolonger secured against axial displacement. As a result, the springs inthe die carrier bias the flange away from the dies and holding bolts,which are secured to the flange and hold the dies in the threadingposition, are axially displaced with the flange and release the diesfrom the threading position.

To limit the axial displacement of the flange and the other partsattached to it, the flange is attached to the die carrier by screwswhich afford a certain length of axial displacement of the flange.

The various features of novelty which characterize the invention arepointed out with particularity in the claims annexed to and forming apart of this disclosure. For a better understanding of the invention,its operating advantages and specific objects attained by its use,reference should be had to the accompanying drawings and descriptivematter in which there are illustrated and described preferredembodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWING In the drawing:

FIG. 1 is a longitudinal sectional view of a device embodying thepresent invention;

FIG. 2 is a partial section of the device shown in FIG. 1; and

FIG. 3 is a partial sectional view of another embodiment of the deviceshown in FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION In FIG. 1 a thread-cutting diehead is illustrated which can be mounted in a ratchet wrench or athreadcutting machine. The thread-cutting die head includes an annularlyshaped axially extending die support member or carrier 1 having anaxially extending bore 12. At one end of the die carrier 1, a pluralityof radial grooves 26 are formed in which thread-cutting dies 2 arepositioned. At the forward end of the die carrier, that is the endcontaining the dies 2, an annular plate 17 is detachably secured to thecarrier by means of bolts 18 and forms a cover over the ends of thegrooves 26.

Each of the threading dies is provided with an obliquely extendingholding groove 2' formed into one of its sides and the holding groovesare equidistantly spaced from the axis of the die carrier 1.Complementary shaped holding cams 3 fit into the holding grooves 2' forsecuring the dies 2 in the threading position. Each holding cam 3 isassociated with a holding bolt 4 and extends outwardly'from the end ofthe holding bolt. The holding bolts are axially movable within a circleof bores'4' formed through the die carrier 1, the circle of the bores isconcentrically arranged about the axis of the die carrier. At theopposite end of the holding bolts 4 from the holding cams 3, lockingsurfaces 27 are provided which engage into corresponding recesses orcutouts in an annular flange 5. The flange 5 is positioned on therearward end of the die carrier 1 and is arranged concentrically aboutits axis.

Extending through the flange 5 into the bore 12 in the die carrier 1 isa slide bushing 6 which is in threaded engagement with the flange. Theslide bushing 6 is axially movably positionable within the bore 12 sothat its threaded engagement with flange can be adjusted.

A sensing bolt 7 extends through the slide bushing 6 from the rearwardend toward the forward end of the die carrier. The forward end of thesensing bolt 7 is positioned forwardly of the end of the slide bushing 6within the bore 12 and has a contact surface 9 at its forward end whichcontacts the juxtaposed end of a workpiece 8 as the threading operationproceeds. The contact surface has a diameter which is smaller than theroot diameter of the thread cut into the workpiece and is larger thanthe inner diameter of the workpiece when it is of a tubular form.Between the contact surface 9 of the sensing bolt and the forward end ofthe slide bushing 6, the sensing bolt has a shoulder 9a which projectsradially outwardly beyond the radially inner surface of the slidebushing 6. Immediately adjacent the shoulder 9a and extending toward therearward end of the sensing bolt is an annular groove 10 which has adiameter smaller than the diameter of the inside surface of the slidebushing 6.

Adjacent the forward end of the slide bushing 6, a number of openings11a each contain a ball 11 which, when the threading dies 2 are in thethreading position, seat within a groove 13 extending annularly aboutthe surface of the bore 12. The diameter of the ball is such that itequals the wall thickness dimension of the slide bushing plus the depth25 of the groove 13. Similarly, the depth 24 of the annular groove 10 inthe sensing bolt measured inwardly from the inner surface of the slidebushing is substantially equal to the depth 25 of the groove 13.Accordingly, when the threading die head is in the threading position,the balls 11 are secured within the groove 13 and provide aninterengagement between the slide bushing 6 and the die carrier 1 sothat the slide bushing is not displaced axially relative to the diecarrier.

As can be seen in FIG. 1, the sensing bolt 7 extends rearwardly beyondthe rearward end of the slide bushing 6 and a securing ring 19 encirclesthe rearward end of the sensing bolt for limiting its stroke. Further, aball and spring device 16 is formed in the lateral surface of thesensing bolt 7 with the ball being biased into a groove or recess in theinner surface of the slide bushing 6 for preventing any accidentaldisplacement of the sensing bolt relative to the slide bushing.

In the flange 5, a safety member extends into locking engagement withthe slide bushing 6 to prevent any relative rotation between the flangeand the slide bushing when the threaded connection between the two hasbeen established.

In the surface of the die carrier 1 juxtaposed to the face of the flange5 directed toward the forward end of the die carrier, are a number ofbores 21 each containing a spring 14. While one spring could be used, itis preferable to employ a number of such springs. The springs 14 arecompressed when the flange is held against the die carrier and thesprings bias the flange in the direction outwardly away from therearward end of the die carrier.

In FIG. 1, one of a number of cams 22 are shown on the outercircumferential surface of the die carrier arranged for engagementwithin a ratchet wrench or a thread-cutting machine. The cams 22 securethe die carrier to the thread-cutting device in the manner of a bayonetclosure so that the threading die head follows the movement of thethread cutting device.

FIG. 1 shows the manner in which the dies 2 are held in the threadingposition as threads are cut in the surface of the workpiece 8. Duringthe threading operation, the slide bushing 6 secured to the die carrier1 by the balls 11 extending into the groove 13 holds the flange 5against the rearward end of the die carrier. With the flange heldagainst the die carrier the holding bolts 4 by means of the cams 3 holdthe threading dies 2 in position. When the threading operation iscompleted, the engagement between the end surface-of the workpiece 8 andthe contact surface 9 of the sensing bolt 7 displaces the sensing bolttoward the rearward end of the die carrier until the annular groove 10in the sensing bolt moves into register in the axial direction with theopenings 11a in the slide bushing 6. When the annular groove 10 and theopenings are in register, the balls 11 are displaced inwardly so thatthe slide bushing 6 is no longer held against axial displacementrelative to the die carrier. With the slide bushing released, thesprings 14 bias the flange outwardly away from the rearward end of thedie carrier and the flange in turn pulls the holding bolts 4 and theirassociated cams 3 from engagement within the grooves 2' of the threadingdies 2 so that the threading dies are released from the threadingposition.

In FIG. 2 a screw 20 is shown extending through a bore 23 in the flange5 into another bore in the die carrier 1. The head of the screw 20extends outwardly from the face of the flange and provides a stopsurface for limiting the axial displacement of the flange and of theholding bolts 4 when the slide bushing is released from its engagementwith the die carrier. While a single screw 20 is shown in FIG. 2, itwill be appreciated that it is preferable to provide a number of suchscrews spaced about the flange.

In FIG. 3 another embodiment of a die carrier 1' is illustrated whichincludes a screw bushing 28 inserted coaxially into the bore of the diecarrier 1'. The screw bushing 28 is inset into the bore of the diecarrier from its rearward end. A slide bushing 6' in threaded engagementwith an annular flange 5, extends into the bore formed by the screwbushing 28. The screw bushing 28 has a threaded portion 31 in threadedengagement with the bore of the die carrier 1' so that it can beadjusted in the axial direction. This axial adjustment provides acontrol over the length of the thread to be cut by the device.

The forward end of the screw bushing 28, that is the end spaced from thethreaded portion 31, is provided with screw slots 32. A safety device 30extends through the wall of the die carrier 1' into engagement with theouter surface of the screw bushing 28 for holding the bushing againstany undesired or unintentional rotation. Forwardly of the annular groove10', in the sensing bolt 7', is a packing or washer 29 disposed aboutthe surface of the sensing bolt for preventing the penetration of dirtand other undesired extraneous matter into the bore of the die carrierwhich affords a guide for the sensing bolt 7'.

ln place of the arrangement shown in FIG. 2, the extent of the axialdisplacement of the flange 5' in FIG. 3, is provided by an enlargeddiameter within the forward interior end of the screw bushing 28 whichaffords a contact shoulder surface 33 at the point where the insidediameter of the screw bushing is reduced and contacts the outer surfaceof the slide bushing 6. Adjacent the forward end of the annular grooveis a collar 34 which extends radially outwardly so that it projects atleast radially outwardly beyond the inner edge of the shoulder surface33. As can be seen in FIG. 3, the ball locking arrangement is providedbetween the slide bushing 6 and the screw bushing 28. When the ball lockis released by the axial displacement of the sensing bolt 7 and the ballenters the annular groove 10, the axial displacement of the sensing bolt7', the slide bushing 6' and the flange 5"are limited by the contactingengagement between the collar 34 on the sensing bolt and the shouldersurface 33 on the screw bushing held within the bore of the die carrier1.

While specific embodiments of the invention have been shown anddescribed on detail to illustrate the application of the inventiveprinciples, it will be understood that the invention may be embodiedotherwise without departing from such principles.

What is claimed is:

l. A threading die head for insertion into a threadcutting machine forcutting threads in a workpiece, said die head including an annularlyshaped die carrier having a bore extending axially therethrough, aplurality of disengageable threading dies mounted in said die carrier,holding cams arranged to secure said threading dies in the threadingposition, and means associated with said cams for releasing said diesfrom the threading position, wherein the improvement comprises that saiddie carrier is axially elongated, a plurality of axially movableangularly spaced holding rods extending axially through said diecarrier, said means for releasing said die comprises an annular flangelocated on one end of said die carrier spaced axially from saiddies andhaving an opening therethrough, means for resiliently biasing saidflange in the axial direction away from said dies, means for securingsaid holding bolts to said flange, a slide bushing positioned within anextending axially through the opening in said flange and the bore insaid die carrier, said slide bushing disposed in detachable engagementwith. said flange, a sensing bolt arranged coaxially within andextending through said slide bushing, said sensing bolt having a contactsurface arranged to engage the workpiece, said sensing bolt having anannular groove formed on its surface'located radially inwardly of theinner surface of said slide bushing, said slide bushing having at leastone opening extending through its wall from its outer to its innersurface, a ball positioned within the opening in said slide bushing andhaving a diameter substantially equal to the wall thickness of saidslide bushing and the depth of the annular groove in said sensing bolt,said die carrier having an annular groove formed in the surface of itsbore and the annular groove in said die carrier has a depthsubstantially equal to the depth of the annular groove in said sensingbolt so that said ball can be seated within said annular groove in saiddie carrier and the opening in said slide bushing, each of said holdingbolts at the ends opposite the end secured to said flange having one ofsaid holding cams mounted thereon, so that with said ball positionedwithin the opening in said slide bushing and in the annular groove insaid die carrier said slide bushing is held against axial displacementrelative to said die carrier with said dies secured in the threadingposition by said holding cams and with the annular groove in saidsensing bolt displaced axially from said opening in said slide bushing,and when said contact surface of said sensing bolt in engagement withthe workpiece displaces said sensing bolt axially within said slidebushing until the annular groove therein is registered opposite theopening in said slide bushing and said ball is displaced inwardly intothe annular groove in said sensing bolt affording axial displacement ofsaid slide bushing and flange relative to said die carrier due to saidmeans for resiliently biasing said flange and the axial displacement ofsaid flange effecting the axial withdrawal of said holding cams fromsaid dies for releasing said dies from the threading position.

2. A threading die head, as set forth in claim 1, characterized in thatwhere a tubular workpiece is to be threaded, the outside diameter of thecontact surface of said sensing bolt is smaller than the root diameterof the thread to be cut and larger than the inside diameter of thetubular workpiece.

3. A threading die head, as set forth in claim 1, wherein said means forresiliently biasing said flange comprises a plurality of bores formed insaid die carrier with the axis of said bores extending in the axialdirection of said die carrier, and a spring positioned within each ofsaid bores and contacting said flange so that said springs bias saidflange inthe axial direction away from said dies.

4. A threading die head, as set forth in claim 1, wherein said flangeand said slide bushing are detachably engaged by a threaded connectiontherebetween, and means for securing said flange to said slide bushingfor preventing relative rotation therebetween.

5. A threading die head, as set forth in claim 4, wherein said means forsecuring said flange and said sliding bushing against relative rotationcomprises a securing device extending through said flange into engagement with said sliding bushing in the range of the threadedconnection therebetween.

6. A threading die head, as set forth in claim 1, wherein a plurality offollower cams mounted on the circumferential periphery of said diecarrier and said die cams arranged for engagement within a threadcuttingdevice in the manner of a bayonet closure for securing said threadingdie head to the thread-cutting device.

7. A threading die head, as set forth in claim 1, wherein said flangehaving at least one opening therethrough with the axis of said openingin parallel relationship with the axis of the bore in said die carrier,a screw positioned within said bore and extending into engagement withsaid die carrier, said screw having a head thereon with a diametergreater than the diameter of the opening in said flange and said headdisposed in axially spaced relationship from the flange in the threadingposition of said threading die head so that said head on said screwaffords a stop surface for limiting the axial displacement of saidflange.

8. A threading die head, as set forth in claim 1, wherein said contactsurface is formed on the end surface of said sensing bolt located closerto the end of said die carrier containing said dies.

9. A threading die head, as set forth in claim 1, wherein a boreextending into said sensing bolt transversely of the axis thereof andwithin the range of said sensing bolt positioned within said slidebushing, aball spring assembly positioned within said bore in saidsensing bolt, and the recess formed in the inner surface of said slidebushing opposite the bore in said sensing bolt so that said ball isspring biased into the recess in said slidebushing for preventingaccidental axial displacement of said sensing bolt relative to saidslide bushing.

10. A threading die head, as set forth in claim 1, wherein said slidebushing having a number of openings therein'and one of said ballslocated within each of said openings for interconnecting said diecarrier and said slide bushing.

11. A threading die head, as set forth in claim 1, wherein a screwbushing is fitted within the bore in said die carrier and is in axiallyadjustable threaded engagement with said die carrier, and said slidebushing extending into said screw bushing and being axially displaceablerelative thereto in releasing said dies from the threading position.

12. A threading die head, as set forth in claim 11, wherein a securingdevice extending transversely through said die carrier into engagementwith said screw bushing for preventing unintentional rotationtherebetween.

13. A threading die head, as set forth in claim 1, wherein said sensingbolt extends axially through said slide bushing with its end more remotefrom said dies extending axially outwardly from said slide bushing, anda securing ring mounted on the end of said sensing bolt which extendsoutwardly from the end of said slide bushing more remote from said dies.

14. A threading die head, as set forth in claim 1, wherein an annularcollar projecting laterally outwardly from said sensing bolt and spacedbetween the end of said slide bushing within the bore in said carrierand the contact surface on said sensing bolt, said annular collarprojecting transversely from said bolt beyond the inner surface of saidslide bushing at its end adjacent said annular collar so that the endsurface of said slide bushing acts as a stop for limiting the axialdisplacement of said sensing bolt.

15. A threading die head, as set forth in claim 1, wherein the oppositeend of said die carrier from the end adjacent said annular flange havinga plurality of angularly spaced radially extending grooves, one of saiddies located in each of said grooves, and an annular cover plateremovably attached to the end of said die carrier for securing said dieswithin said grooves.

16. A threading die head, as set forth in claim 1, wherein said means onsaid holding bolts for securing said bolts to said flange comprisessurfaces formed on the ends of said bolts and extending laterallyoutwardly therefrom, and recesses formed in said flange for receivingthe surfaces on said holding bolt for securing said holding bolts tosaid flange.

1. A threading die head for insertion into a thread-cutting machine forcutting threads in a workpiece, said die head including an annularlyshaped die carrier having a bore extending axially therethrough, aplurality of disengageable threading dies mounted in said die carrier,holding cams arranged to secure said threading dies in the threadingposition, and means associated with said cams for releasing said diesfrom the threading position, wherein the improvement comprises that saiddie carrier is axially elongated, a plurality of axially movableangularly spaced holding rods extending axially through said diecarrier, said means for releasing said die comprises an annular flangelocated on one end of said die carrier spaced axially from said dies andhaving an opening therethrough, means for resiliently biasing saidflange in the axial direction away from said dies, means for securingsaid holding bolts to said flange, a slide bushing positioned within anextending axially through the opening in said flange and the bore insaid die carrier, said slide bushing disposed in detachable engagementwith said flange, a sensing bolt arranged coaxially within and extendingthrough said slide bushing, said sensing bolt having a contact surfacearranged to engage the workpiece, said sensing bolt having an annulargroove formed on its surface located radially inwardly of the innersurface of said slide bushing, said slide bushing having at least oneopening extending through its wall from its outer to its inner surface,a ball positioned within the opening in said slide bushing and having adiameter substantially equal to the wall thickness of said slide bushingand the depth of the annular groove in said sensing bolt, said diecarrier having an annular groove formed in the surface of its bore andthe annular groove in said die carrier has a depth substantially equalto the depth of the annular groove in said sensing bolt so that saidball can be seated within said annular groove in said die carrier andthe opening in said slide bushing, each of said holding bolts at theends opposite the end secured to said flange having one of said holdingcams mounted thereon, so that with said ball positioned within theopening in said slide bushing and in the annular groove in said diecarrier said slide bushing is held against axial displacement relativeto said die carrier with said dies secured in the threading position bysaid holding cams and with the annular groove in said sensing boltdisplaced axially from said opening in said slide bushing, and when saidcontact surface of said sensing bolt in engagement with the workpiecedisplaces said sensing bolt axially within said slide bushing until theannular groove therein is registered opposite the opening in said slidebushing and said ball is displaced inwardly into the annular groove insaid sensing bolt affording axial displacement of said slide bushing andflange relative to said die carriEr due to said means for resilientlybiasing said flange and the axial displacement of said flange effectingthe axial withdrawal of said holding cams from said dies for releasingsaid dies from the threading position.
 2. A threading die head, as setforth in claim 1, characterized in that where a tubular workpiece is tobe threaded, the outside diameter of the contact surface of said sensingbolt is smaller than the root diameter of the thread to be cut andlarger than the inside diameter of the tubular workpiece.
 3. A threadingdie head, as set forth in claim 1, wherein said means for resilientlybiasing said flange comprises a plurality of bores formed in said diecarrier with the axis of said bores extending in the axial direction ofsaid die carrier, and a spring positioned within each of said bores andcontacting said flange so that said springs bias said flange in theaxial direction away from said dies.
 4. A threading die head, as setforth in claim 1, wherein said flange and said slide bushing aredetachably engaged by a threaded connection therebetween, and means forsecuring said flange to said slide bushing for preventing relativerotation therebetween.
 5. A threading die head, as set forth in claim 4,wherein said means for securing said flange and said sliding bushingagainst relative rotation comprises a securing device extending throughsaid flange into engagement with said sliding bushing in the range ofthe threaded connection therebetween.
 6. A threading die head, as setforth in claim 1, wherein a plurality of follower cams mounted on thecircumferential periphery of said die carrier and said die cams arrangedfor engagement within a thread-cutting device in the manner of a bayonetclosure for securing said threading die head to the thread-cuttingdevice.
 7. A threading die head, as set forth in claim 1, wherein saidflange having at least one opening therethrough with the axis of saidopening in parallel relationship with the axis of the bore in said diecarrier, a screw positioned within said bore and extending intoengagement with said die carrier, said screw having a head thereon witha diameter greater than the diameter of the opening in said flange andsaid head disposed in axially spaced relationship from the flange in thethreading position of said threading die head so that said head on saidscrew affords a stop surface for limiting the axial displacement of saidflange.
 8. A threading die head, as set forth in claim 1, wherein saidcontact surface is formed on the end surface of said sensing boltlocated closer to the end of said die carrier containing said dies.
 9. Athreading die head, as set forth in claim 1, wherein a bore extendinginto said sensing bolt transversely of the axis thereof and within therange of said sensing bolt positioned within said slide bushing, a ballspring assembly positioned within said bore in said sensing bolt, andthe recess formed in the inner surface of said slide bushing oppositethe bore in said sensing bolt so that said ball is spring biased intothe recess in said slide bushing for preventing accidental axialdisplacement of said sensing bolt relative to said slide bushing.
 10. Athreading die head, as set forth in claim 1, wherein said slide bushinghaving a number of openings therein and one of said balls located withineach of said openings for interconnecting said die carrier and saidslide bushing.
 11. A threading die head, as set forth in claim 1,wherein a screw bushing is fitted within the bore in said die carrierand is in axially adjustable threaded engagement with said die carrier,and said slide bushing extending into said screw bushing and beingaxially displaceable relative thereto in releasing said dies from thethreading position.
 12. A threading die head, as set forth in claim 11,wherein a securing device extending transversely through said diecarrier into engagement with said screw bushing for preventingunintentional rotation therebetween.
 13. A threading die head, as setforth in claim 1, wherein said sensing bolt extends axially through saidslide bushing with its end more remote from said dies extending axiallyoutwardly from said slide bushing, and a securing ring mounted on theend of said sensing bolt which extends outwardly from the end of saidslide bushing more remote from said dies.
 14. A threading die head, asset forth in claim 1, wherein an annular collar projecting laterallyoutwardly from said sensing bolt and spaced between the end of saidslide bushing within the bore in said carrier and the contact surface onsaid sensing bolt, said annular collar projecting transversely from saidbolt beyond the inner surface of said slide bushing at its end adjacentsaid annular collar so that the end surface of said slide bushing actsas a stop for limiting the axial displacement of said sensing bolt. 15.A threading die head, as set forth in claim 1, wherein the opposite endof said die carrier from the end adjacent said annular flange having aplurality of angularly spaced radially extending grooves, one of saiddies located in each of said grooves, and an annular cover plateremovably attached to the end of said die carrier for securing said dieswithin said grooves.
 16. A threading die head, as set forth in claim 1,wherein said means on said holding bolts for securing said bolts to saidflange comprises surfaces formed on the ends of said bolts and extendinglaterally outwardly therefrom, and recesses formed in said flange forreceiving the surfaces on said holding bolt for securing said holdingbolts to said flange.